TORONTO – Onex Corp (TSX:OCX) and its affiliates have sold their remaining 8.4 million shares of Spirit AeroSystems Holdings, Inc. (NYSE:SPR), a former Boeing manufacturing unit that makes major structures for commercial, military and business jets.

Based on the Thursday closing price for Spirit’s shares at the New York Stock Exchange, the Onex Group’s shares would be worth US$304 million but the stock was sold at a slight discount — a common practice when large volumes are sold at once.

Spirit AeroSystems closed at US36.21 on the New York Stock Exchange. The company said the shares owned by the Onex Group were sold for $35.90 — a discount of 31 cents per share.

In Toronto, Onex shares closed at C$63.25. They hit a 52-week high of $63.54 on June 2.

Toronto-based Onex is a highly diversified company, which invests on behalf of itself and partners in various industries. A significant portion of its profits come from the purchase and resale of companies after a period of control.

Its sale of the remaining stake in Spirit AeroSystems follows the sale of The Warranty Group in a deal valued at US$1.5 billion to an affiliate of TPG Capital and an agreement to buy York Risk Services Group in a deal valued at US$1.325 billion.

Onex and its affiliates originally acquired Spirit AeroSystems in June 2005.

Over the following nine years, Onex and its affiliates have received US$3.2 billion in proceeds from the investment.

Onex said Thursday that its own original investment in Spirit was US$108 million and its share of the proceeds since 2005, including $118 million of interest, totalled US$975 million.

The sale was announced in Toronto by Onex senior managing director Seth Mersky and by Spirit from Wichita, Kan., where its main operations are located.

Spirit said current and former members of its management would also be part of the secondary public offering of nearly 8.56 million class A common shares for $35.90 each.